Control device, system and process for operating electrochemical gas generator cells

ABSTRACT

A control device (10, 20), for actuating an electrochemical gas generator cell (11), is configured to output a first control signal (Igen), which brings about the generation of an electrical operating voltage at the electrochemical gas generator cell (11), for an operating phase of the electrochemical gas generator cell (11). The electrical operating voltage is at least equal to an electrolysis voltage (Uele) of the electrochemical gas generator cell (11). The control device (10, 20) is further configured to output a second control signal (IRuhe, Upre), which brings about the generation of an electrical bias voltage (Upre) at the electrochemical gas generator cell (11), for a rest phase of the electrochemical gas generator cell (11). The electrical bias voltage (Upre) is lower than the electrolysis voltage (Uele). Further aspects pertain to systems (40a) and processes (50, 60, 70) for operating electrochemical gas generator cells (110).

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority under 35 U.S.C. § 119 of German Application 10 2019 005 612.4, filed Aug. 9, 2019, the entire contents of which are incorporated herein by reference.

TECHNICAL FIELD

Exemplary embodiments pertain to control devices for actuating electrochemical gas generator cells and to systems for operating electrochemical gas generator cells as well as for generating gases. Further exemplary embodiments pertain to processes for operating electrochemical gas generator cells.

TECHNICAL BACKGROUND

Gas generators or gas generator cells may be used to test the ability of gas sensors to function. For example, it may be necessary to test such gas generators periodically over time to determine whether they function properly (so-called bump tests). For example, electrochemical gas generators may be used for these bump tests.

Such gas generators comprise, in general, a generator electrode for generating a gas (e.g., test gas) and a counterelectrode for completing the electrolysis cell or generator cell. The two electrodes are in contact with one another in a common electrochemical cell via an electrolyte, which may be, e.g., a liquid or gel-like electrolyte. Moreover, additional chemicals, which contribute to the generation of the test gas, may be provided in the electrode material and/or directly on the electrode material.

For example, a substance contained in or added to the electrolyte is converted during the generation of the test gas into a test gas by means of electrolysis or the generator electrode itself consists of (or comprises) a material that can be converted into test gas by means of electrolysis. The generation of the test gas or the test phase (e.g., operating phase) of the generator cell is started and ended, e.g., by controlling a flow of current through the gas generator cell. The electrolysis may be driven and controlled by means of direct current.

A potential, which is characteristic of the chemical nature of the gas generator cell and which is higher than a minimum potential U_(ele) (e.g., electrolysis potential or electrolysis voltage of the generator cell) necessary for the electrolysis, becomes established on the cell during the operation, e.g., when an operating current is being applied to the generator cell. This minimum electrolysis potential U_(ele) depends, e.g., on the reactions involved in the generation of the test gas and on the electrochemical series.

It may be necessary when using electrochemical gas generator cells for testing gas sensors to generate a predefined, exact quantity of test gas in a short time in order to carry out a reproducible sensor test and to make it possible to use the sensor again as soon as possible. However, a duration until the generation of a test gas may be long or different quantities of test gas may be generated in different test cycles in the case of prior-art concepts for operating electrochemical gas generator cells. Further, the operation of electrochemical gas generator cells may be energy-intensive, so that the battery has to be replaced or charged already after a relatively short time, for example, in the case of battery-operated gas generation systems or sensor testing devices with electrochemical gas generator cell.

SUMMARY

One object is therefore to provide concepts for an improved operation of electrochemical gas generator cells.

The object is accomplished according to the subjects of the independent patent claims. Further aspects and variants of the present invention, which can lead to additional advantages, are described in the dependent claims, in the following description as well as in connection with the figures shown.

A control device for actuating an electrochemical gas generator cell is proposed to this end. The control device is configured to output a first control signal (e.g., a control signal for setting a current signal or a current signal, e.g., an operating current), which brings about the generation of an electrical operating voltage at the electrochemical gas generator cell, for an operating phase of the electrochemical gas generator cell. The electrical operating voltage is at least equal to an electrolysis voltage of the electrochemical gas generator cell, so that the electrochemical gas generator cell generates a gas.

Further, the control device is configured to output a second control signal (e.g., control signal for setting an electrical current and/or an electrical voltage, e.g., a current and/or voltage signal), which brings about the generation of an electrical bias voltage (e.g., predefined electrical bias voltage) at the electrochemical gas generator cell, for a rest phase of the electrochemical gas generator cell. The electrical bias voltage is lower than the electrolysis voltage.

The electrical bias voltage can be reached during the rest phase, for example, by applying a zero signal current (e.g., a current with low current intensity) to the electrochemical gas generator cell. For example, the electrical voltage present at the electrochemical gas generator cell can be measured and the zero signal current can be set (e.g., regulated or controlled) such that the intended electrical bias voltage becomes established at the electrochemical gas generator cell. For example, a current regulation with feedback can be used or a predefined current can be set by means of a control without feedback. It is possible, as an alternative, for example, to provide the electrical bias voltage by applying a corresponding electrical voltage to the electrochemical gas generator cell.

It is proposed (e.g., contrary to other concepts) not to simply switch off the gas generator cell or the gas generator during the rest phase (e.g., between two test cycles or bump tests, e.g., operating phases), during which no gas shall be generated, but to operate it in a resting mode, in which (e.g., at least during a part of the rest phase) the electrical bias voltage is present at the electrochemical gas generator cell. It may be possible in this manner to maintain the electrochemical gas generator cell in a defined state, e.g., voltage state, during the rest phase.

After switching off the operating current for generating gas, the voltage present at the electrochemical gas generator cell usually drops (e.g., with the use of other concepts for operating generator cells) until it reaches a base voltage (e.g., in a state of equilibrium of the electrochemical gas generator cell) after a variable duration (e.g., depending on various external factors). When the operating current is applied again to the generator cell (e.g., for a predefined electrolysis time), a capacitive current will flow at first during an activation phase until the electrolysis voltage is reached again. The gas can be generated in a subsequent operating phase until the operating current is switched off again after the end of the electrolysis time. Depending on the initial state of the electrochemical gas generator cell (e.g., value of the electrical voltage at the cell, which may be between the base voltage and electrolysis voltage), the duration of the activation phase can vary and the quantity of the gas generated during the operating phase can thus vary as well.

By contrast, it can be achieved by the use of the bias voltage proposed during the rest phase that the voltage present at the electrochemical gas generator cell is known precisely and/or can be set. For example, the percentage of the activation phase relative to the duration of the electrolysis time and consequently the quantity of gas generated during the electrolysis time are known as a result. The control device can thus make it possible to generate a precisely defined quantity of gas during an operating phase by means of the generator cell.

Provisions may be made, in particular, for the electrical bias voltage (e.g., a mean value of the electrical bias voltage) to equal at least 30% (or at least 40%, at least 50%, at least 60%, at least 70%, at least 80%, at least 90% or at least 95%) of the electrolysis voltage. It can be achieved hereby that when the operating current is switched on, a smaller quantity of capacitive current must flow until the electrolysis voltage is reached and the generation of gas starts. In other words, the duration of the activation phase can be reduced when a higher electrical bias voltage is used. In case of a longer activation phase, only a smaller quantity of gas can, by contrast, be generated with the use of the same electrolysis time, because no gas is still being generated during the activation phase (during the flow of the capacitive current).

It is favorable, for example, when operating the gas generator for bump tests of gas sensors to generate the test gas to be generated in the shortest possible time, so that the tested sensor will, for example, be able to be used again as quickly as possible. By using a high bias voltage during the rest phase (e.g., between two bump tests), the activation phase can be reduced, so that, contrary to other concepts, an equal quantity of test gas can be generated during a globally shorter time after switching on the operating current. A more accurately reproducible quantity of gas can thus be generated by means of the bias voltage during a reduced time.

For example, the second control signal may be constant over time. The first control signal may be, for example, a direct current, which is configured as an operating current for generating the gas. When using a d.c. current source, this can be regulated down in respect to the current intensity during the rest phase in order to generate a constant zero signal current with a lower current intensity. As a result, it is advantageously possible, for example, to use a single current source for the operation during the operating phase and during the rest phase. As an alternative, the second control signal may have a ripple content (e.g., alternating signal with offset). For example, it is possible to achieve above-described effects with a constant electrical bias voltage and/or with an electrical bias voltage with a ripple content, which effects are made possible by the bias voltage.

The electrical bias voltage is lower than the electrolysis voltage of the electrochemical gas generator cell by at least 100 mV (or by at least 200 mV, by at least 300 mV, by at least 500 mV, by at least 700 mV, or by at least 900 mV) or it is lower than the electrolysis voltage of the electrochemical gas generator cell by at most 1.5 V (or by at most 1 V or by at most 500 mV). For example, a faster change from the rest phase to the generation of gas can be made possible by an electrical bias voltage, which is only slightly lower than the electrolysis voltage.

As was mentioned already, the first control signal may comprise a first current signal (e.g., operating current for generating gas) for the electrochemical gas generator cell. The second control signal may be a second current signal (e.g., zero signal current for generating the bias voltage) for the electrochemical gas generator cell. The second current signal, e.g., the zero signal current, has, for example, a current intensity of at most 5% (or at most 3%, at most 1%, at most 0.5%, or at most 0.1%) of a current intensity of the first current signal (e.g., of the operating current). The current intensity of the second current signal may be regulated, for example, based on a voltage measurement at the electrochemical gas generator cell, so that the predefined electrical bias voltage becomes established at the electrochemical gas generator cell. The zero signal current can flow, e.g., continuously during the rest phase and/or it may be configured as a pulse signal (e.g., by means of pulse width modulation), e.g., in order to maintain the voltage of the generator cell within a defined voltage range, e.g., by means of a periodic charging of the generator cell to just below the electrolysis voltage and by means of a subsequent lowering of the cell voltage until a next charging time (e.g., when a defined lower limit voltage is reached on the basis of the usual voltage drop of the generator cell).

For example, the second current signal (e.g., the zero signal current, e.g., a continuous current signal) may have a mean value of at least 10 nA (or at least 20 nA, at least 50 nA, at least 100 nA, at least 300 nA, at least 500 nA or at least 1 μA) and/or at most 10 μA (or at most 5 μA, at most 3 μA or at most 1 μA).

As was mentioned already, the electrical bias voltage can be reached, as an alternative, by applying a corresponding electrical voltage to the electrochemical gas generator cell during the rest phase. The control device may accordingly comprise a current source for generating the first control signal as an operating current for the electrochemical gas generator cell and further a voltage source for generating the second control signal (e.g., electrical voltage) as an electrical bias voltage. The control device may comprise, furthermore, a switch, which is configured for switching an electrical connection between the current source and the electrochemical gas generator cell or between the voltage source and the electrochemical gas generator cell.

For example, the switch can connect the electrochemical gas generator cell to the current source (e.g., d.c. current source) during the operating phase in order to bring about a galvanostatic operation of the electrochemical gas generator cell. The switch can be switched during the rest phase (e.g., controlled by means of the control device) in order to connect the electrochemical gas generator cell to the voltage source and to bring about a potentiostatic operation, during which the bias voltage is present at the electrochemical gas generator cell.

The control device is configured, for example, to set an output voltage (e.g., mean output voltage) of the voltage source at a value lower than the electrolysis voltage and/or to set it at a value of at least 30% (or at least 60%, at least 70%, at least 80% or at least 90%) of the electrolysis voltage.

The control device may comprise, for example, a measuring device for measuring an electrical voltage present at the electrochemical gas generator cell. As a result, it is possible, e.g., to adjust the zero signal current and/or to determine the value of the electrolysis voltage of the electrochemical gas generator cell.

As was mentioned, the control device may comprise, e.g., a d.c. current source for generating the operating current for the electrochemical gas generator cell and a voltage supply (e.g., comprising a controllable voltage source) for the d.c. current source. The voltage supply can provide the energy needed to operate the d.c. current source. The control device may be configured to regulate a supply voltage of the voltage supply during the operating phase and/or during the rest phase to a predefined value of at most 200% (or at most 150%, at most 125%, 120%, at most 115%, at most 110% or at most 105%) of an electrical voltage present at the electrochemical gas generator cell. For example, the supply voltage may be regulated to at most 125% of the electrolysis voltage. In other words, the control device may be configured for the adaptive adjustment of the supply voltage of the d.c. current source to the lowest possible value, which is nevertheless still sufficiently high for the operation of the generator cell.

It is possible, for example, to reduce power losses at the control device by an adaptive setting of the supply voltage of the d.c. current source during the operating phase. For example, the supply voltage regulated to the predefined value is sufficient for reaching the electrolysis voltage at the electrochemical gas generator cell and thus for the generation of gas. By contrast, for example, higher energy losses occur in the case of other concepts, in which a gas can be generated without adaptive adjustment of the supply voltage to the voltage of the generator cell. It can be achieved by lower electrical losses, e.g., during bump tests of gas sensors, that an energy storage device (e.g., a battery) of a testing device with the control device and with an electrochemical gas generator cell must be replaced or charged less frequently.

The electrochemical gas generator cell may be configured, for example, to generate a gas comprising at least one of the gases hydrogen sulfide, hydrogen, ammonia or chlorine. For example, a geometric surface of electrodes of the generator cell may be in the range of a few square cm (e.g., smaller than 10 cm², smaller than 5 cm², smaller than 3 cm² or smaller than 1 cm²) and/or larger than 0.1 cm² (or larger than 0.5 cm² or larger than 1 cm²).

Further, a system for operating an electrochemical gas generator cell is proposed. The system comprises a d.c. current source, which is configured to apply an operating current to the electrochemical gas generator cell. The system further comprises a voltage supply of the d.c. current source or for the d.c. current source and a control device for controlling the voltage supply for the d.c. current source. The control device is configured to regulate a supply voltage of the voltage supply to a predefined value of at most and/or typically 125% of a voltage present at the electrochemical gas generator cell (e.g., during an operating phase of the electrochemical gas generator cell). For example, the supply voltage may be selected to be somewhat higher than the voltage present at the electrochemical gas generator cell in order to always guarantee the generation of gas.

The system being proposed can make it possible to operate a gas generator during an operating phase (e.g., for bump tests of gas sensors) with reduced electrical losses. For example, the system is provided in a mobile device (e.g., a portable, battery-operated testing device) and can cause, for example, a battery change to be needed less frequently, because it is possible, for example, to reduce needless power losses at the d.c. current source.

For example, the system comprises a measuring device for measuring an electrical voltage present at the electrochemical gas generator cell. As a result, it can be made possible to adaptively adjust the supply voltage. The electrolysis voltage of the electrochemical gas generator cell may change, e.g., due to age. Based on the possibility of voltage measurements, the power loss can be reduced during the operation and the functionality of the electrochemical gas generator cell (e.g., generation of gas) can be guaranteed at the same time, because it is always possible to set a voltage necessary for the electrolysis.

The control device is configured, for example, to adjust the supply voltage of the voltage supply based on a voltage measurement provided by the measuring device during the operating phase of the electrochemical gas generator cell. An adaptive regulation of the supply voltage may be advantageous precisely during a switch-on phase, because the voltage at the electrochemical gas generator cell may change relatively greatly during this time. The adjustment of the supply voltage may be carried out continuously or quasi-continuously (e.g., at a frequency greater than 10 Hz, greater than 50 Hz or greater than 100 Hz).

The control device may comprise, for example, a memory, in which the predefined value of the supply voltage is stored (e.g., typical electrolysis voltage of the generator cell to be operated) and/or can be stored. For example, the necessary supply voltage can be determined and stored during a first operating phase, so that it is directly available for subsequent operating phases. For example, the supply voltage may be adaptively adjusted to the electrolysis voltage of the electrochemical gas generator cell. This may be advantageous because the electrolysis voltage and hence the voltage present at the electrochemical gas generator cell during the operating phase may change (e.g., based on aging processes). A current value of the necessary supply voltage can always be directly available due to the storage of a respective voltage value (e.g., of the current electrolysis voltage) for each operating phase, e.g., during the respective next operating phase.

The system may be configured to generate a zero signal current of less than 300 nA, e.g., during a rest phase, and/or to generate an operating current of at least 1 mA to be applied to the electrochemical gas generator cell, e.g., during an operating phase.

The system may advantageously have at least one electrochemical gas generator cell. By providing the electrochemical gas generator cell in the system, the control device can be adapted, e.g., to the respective generator cell.

Another aspect pertains to a system for generating a gas with at least one control device described above or below (and/or with features of the above-described system for operating the electrochemical gas generator cell) and with at least one electrochemical gas generator cell. The system comprises, for example, two or more control devices. For example, two control devices are provided in a common housing (e.g., generator housing) of the system. The electrochemical gas generator cell may have, e.g., a generator electrode and a counterelectrode. The electrochemical gas generator cell may have, for example, at least two generator electrodes and a common counterelectrode of the two generator electrodes. Any desired number of generator electrodes and (e.g., at least partly common) counterelectrodes, e.g., x generator electrodes and y counterelectrodes, may be provided, where x, y are selected from natural numbers. For example, the electrochemical gas generator cell may have two, three or more generator electrodes and/or two, three or more counterelectrodes. For example, exactly one counterelectrode may be associated with each generator electrode or a common counterelectrode may be associated with a plurality of (e.g., two or three) generator electrodes. For example, a separate current source may be provided in the system for each generator electrode for operating the respective generator electrode. The control device may actuate, for example, the respective current sources of the respective generator electrodes separately. For example, different control devices may be associated with different generator electrodes.

Another aspect pertains to a process for operating an electrochemical gas generator cell, which is configured to generate a gas in the presence of an electrical voltage higher than an electrolysis voltage of the electrochemical gas generator cell. The process comprises the application of an electrical current to the electrochemical gas generator cell during an operating phase in order to increase a voltage at the electrochemical gas generator cell at least to the electrolysis voltage. The process further comprises a reduction of the electrical current to a zero signal current during a rest phase in order to stop the generation of gas. An electrical bias voltage, which is lower than the electrolysis voltage and equals at least 60% of the electrolysis voltage, is obtained in this case at the electrochemical gas generator cell according to the process based on the zero signal current during the rest phase. The process can make it possible, for example, to generate gas in a shorter time and/or with a precisely defined quantity of gas.

For example, a current intensity of a current source for generating the electrochemical gas generator cell can be reduced in order to reduce the current. The voltage at the electrochemical gas generator cell can be measured in this case and the current intensity can be reduced to the extent that the predefined bias voltage becomes established. As an alternative, the predefined bias voltage can be applied (e.g., by means of a voltage source) to the electrochemical gas generator cell in order to reduce the electrical current, so that the zero signal current flowing through the electrochemical gas generator cell can be obtained based on the bias voltage.

Further, another process for operating an electrochemical gas generator cell is proposed, which comprises the application of an electrical current to the electrochemical gas generator cell by means of a d.c. current source during an operating phase in order to generate the gas and the setting of a supply voltage of the d.c. current source to a value of at most 125% of a voltage present at the electrochemical gas generator cell. For example, energy-efficient operation of the generator cell can be made possible hereby.

Variants of the systems and processes for operating gas generator cells pertain to features of variants as they are described in connection with the control device. A repeated description will not therefore be given and the corresponding features are also considered to have been disclosed in connection with the systems and processes. Further aspects of the present invention are also disclosed in connection with the following examples shown in combination with the figures.

Some examples of devices and/or processes will be explained in more detail below only as examples with reference to the attached figures. The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which preferred embodiments of the invention are illustrated.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a schematic view of a system with an electrochemical gas generator cell, with an electrical current source and with a microcontroller;

FIG. 2 is a schematic view of a system with an electrochemical gas generator cell, with an electrical power source and with an electrical bias voltage source;

FIG. 3 is a schematic view with charge quantities available for gas generation in two different operating modes of an electrochemical gas generator;

FIG. 4 is a schematic view of a system with an electrochemical gas generator cell, with an electrical current source and with a settable voltage source;

FIG. 5 is a flow chart of a process for operating a generator cell comprising the use of a zero signal current during a rest phase;

FIG. 6 is a flow chart of a process for operating a generator cell comprising a regulation of a supply voltage of a current source for generating an operating current for the generator cell; and

FIG. 7 is a flow chart of a process for the adaptive setting of a supply voltage of a current source for operating an electrochemical gas generator.

DESCRIPTION OF PREFERRED EMBODIMENTS

Referring to the drawings, various examples will be described in more detail with reference to the attached figures, in which some examples are shown. The thicknesses of lines, layers and/or areas may be exaggerated for illustration in the figures.

While further examples are suitable for different modifications and alternative forms, some specific examples thereof are correspondingly shown in the figures and will be described in detail below. However, this detailed description does not limit further examples to the specific forms described. Further examples can cover all modifications, corresponding examples and alternatives, which fall within the framework of the disclosure. Identical or similar reference numbers pertain in the entire description of the figures to identical or similar elements, which may be identical to one another or may be implemented in a modified form in the entire description of the figures, while they provide the same or similar function.

It is apparent that if an element is described as being “connected” or “coupled” to another element, the elements may be connected or coupled directly or via one or more intermediate elements. If two elements A and B are combined with the use of an “or,” this shall be understood to mean that all possible combinations are disclosed, i.e., A only, B only as well as A and B, unless something else is explicitly or implicitly defined. An alternative formulation for the same combinations is “at least one of A and B” or “A and/or B.” The same applies, mutatis mutandis, to combinations of more than two elements.

The terminology that is used here to described certain examples shall not be limiting for other examples. If a singular form, e.g., “a, an” and “the” is used, and the use of an individual element is not defined as being obligatory either explicitly or implicitly, further examples may also use plural elements in order to implement the same function. If a function is described below as being implemented with the use of a plurality of elements, further examples may implement the same function with the use of a single element or of a single processing entity. It is further obvious that the terms “comprises,” “comprising,” “has” and/or “having” specify, when used, the presence of the indicated features, integers, steps, operations, processes, elements, components and/or of a group thereof, but they do not rule out the presence or the addition or one or more other features, integers, steps, operations, processes, elements, components and/or group thereof.

Unless defined otherwise, all terms (including technical and scientific terms) are used here in their usual meaning as used in the field to which examples belong.

FIG. 1 shows a schematic view of a system 10 a with an electrochemical gas generator cell 11, with an electrical current source 12 and with a control element, here configured as a microcontroller 13. The microcontroller 13 and/or the current source 12 may form a control device 10 for the electrochemical gas generator cell 11.

The microcontroller 13 can send a control signal I_(gen_Soll) to the current source 12 in order to generate a flow of current (e.g., generator current I_(gen)) through the electrochemical gas generator cell 11 by means of the current source 12. An operating mode of the electrochemical gas generator cell 11, in which a sufficient current flows through the electrochemical gas generator cell 11 in order to generate a gas, is called galvanostatic operation. After the current source 12 has been switched on, a capacitive current I_(gen) can flow at first, which brings about the build-up of a voltage at the electrochemical gas generator cell 11 (increasing the generator voltage U_(gen)). As soon as the voltage U_(gen) present at the electrochemical gas generator cell 11 reaches an electrolysis voltage of the electrochemical gas generator cell 11, this generates a gas. By maintaining an operating current through the electrochemical gas generator cell 11, the gas can be generated, for example, until the current flow is reduced or stopped and the voltage at the electrochemical gas generator cell 11 drops below the electrolysis voltage.

The system 10 a shown is configured not to switch off the current source 12 completely during a rest phase of the electrochemical gas generator cell 11 (in which, e.g., no gas is generated, e.g., when no operating current is flowing through the gas generator cell 11), but to continue to allow a low current flow (e.g., zero signal current) through the electrochemical gas generator cell 11. The microcontroller 13 may send to this end a corresponding control signal to the current source 12 and alternate, e.g., a current flow between operating current and zero signal current. Based on the lower zero signal current, which may, for example, be markedly lower than the operating current, it is possible to lower the voltage at the electrochemical gas generator cell 11 (e.g., slightly) to below the electrolysis voltage and to maintain it at this value. The voltage that can be reached in this manner during the rest phase of the electrochemical gas generator cell 11 can be called the electrical bias voltage at the electrochemical gas generator cell 11.

The voltage U_(gen) present at the electrochemical gas generator cell 11 can be measured, for example, by means of the microcontroller 13 (or of another measuring device). Using a measuring resistor 14, a current flow I_(gen) through the electrochemical gas generator cell 11 can be measured based on a measuring voltage U_(Igen) and a resistance value of the measuring resistor 14. The measured values can be used by the microcontroller 13 to regulate the current source 12 (e.g., in order to set the predefined bias voltage during the rest phase by means of a regulation of the zero signal current).

Contrary to other concepts, the electrical bias voltage makes possible, e.g., a defined state of the electrochemical gas generator cell 11 during the rest phase. It is therefore possible with the use of the bias voltage to more accurately predict, when the operating current is switched on during an operating phase, the time starting from which gas is generated after the switching on. For example, a quantity of generated gas can be checked more accurately. Further, gas can be generated, e.g., in a shorter time, because less capacitive current must flow until the electrolysis voltage is reached starting from the bias voltage.

The galvanostatically controlled gas generation or electrolysis cell (e.g., electrochemical gas generator cell 11) is not switched off in the embodiment shown in FIG. 1 between operating phases (e.g., during the rest phase), e.g., between so-called bump tests for testing a gas sensor, but the electrolysis current I_(gen) is lowered to a lower value (e.g., the lowest possible value) (e.g., a current intensity between 10 nA and 10 μA) (cf. also FIG. 3). The rest of the circuit of the gas generator cell in this case ensures a residual voltage difference U_(pre) (e.g., bias voltage at the electrochemical gas generator cell 11) between the electrodes, which is, e.g., close to the electrolysis potential of the cell. This makes it possible, for example, that the value of the potential of the generator electrodes must only be increased, e.g., by a few mV during the repeated use of the cell in order for the electrolysis and hence the generation of gas to start (e.g., immediately), without any delays possibly occurring based on double layer effects or surface reactions. Examples of time curves of the cell current and of the cell voltage are shown in FIG. 3 (cf. the dash-dotted lines of the diagrams shown in FIG. 3).

FIG. 2 shows a schematic view of a system 20 a with an electrochemical gas generator cell 11, with an electrical current source 12 and with an electrical bias voltage source 21.

The system 20 a shows an alternative possibility of applying a defined bias voltage to the electrochemical gas generator cell 11 during a rest phase. The system 20 a provides the bias voltage source 21 and a switch S to this end. For example, the microcontroller 13, the current source 12, the bias voltage source 21 and/or the switch S may form a control device 20 for the electrochemical gas generator cell 11.

In the embodiment shown in FIG. 2, the electrodes of the electrochemical gas generator cell 11 are connected for the operation of the electrochemical gas generator cell to a control circuit, which makes it possible to switch over between potentiostatic operation (e.g., during the rest phase) and galvanostatic operation (e.g., during the operating phase). The switching is brought about by the switch S, which is controlled by means of the microcontroller 13. The generator electrode is maintained here during the pauses in the potentiostatic operating mode at a potential U_(pre) (e.g., bias voltage), whose value is lower, for example, by only a few mV (e.g., 5-200 mV) than the potential U_(ele) (e.g., electrolysis potential) necessary for the electrolysis. The potential U_(pre) may be set, e.g., via the microcontroller 13 and may also comprise, e.g., as an alternative to a d.c. voltage, an a.c. voltage or a d.c. voltage with superimposed a.c. voltage.

In order to start, for example, a bump test, a switching is carried out (e.g., controlled by means of the microcontroller 13) from the potentiostatic operation, so that, e.g., a constant flow of current I_(gen) is forced to take place over the electrodes in a so-called galvanostatic control of the electrodes and the electrolysis is carried out as a result to generate the gas (e.g., test gas for the bump test) after reaching the electrolysis voltage U_(ele). The current I_(gen) can likewise be set via the microcontroller 13 and may comprise, just like the potential U_(gen), an alternating signal. The value of the potential of the generator electrode increases in the process, e.g., by only a few mV and the electrolysis and hence the generation of gas can start shortly thereafter (e.g., sooner compared to other concepts), so that delays due, e.g., to double layer effects or surface reactions are, for example, minimized or maintained at a constant value. The generator potential U_(gen) is measured by means of the microcontroller 13, just like the generator current I_(gen), which is converted via the current-measuring resistor 14 (R_(Shunt)) into a measured voltage U_(Igen). Contrary to concepts that do not provide a bias voltage during the rest phase, a charge Q₂ available for the gas generation may, for example, be greater as a result (cf. FIG. 3) than a charge Q₁ that can be reached by means of another control. The current and voltage curves for the operation of the electrochemical gas generator cell 11 in the system 20 being described are schematically shown in FIG. 3 on the basis of a dash-dotted line.

The concepts shown in combination with FIG. 1 or FIG. 2 can make possible, for example, during the rest phase (e.g., maintenance time between two gas generation phases) the provision of a constant potential (e.g., electrical bias voltage) at the electrochemical gas generator cell. For example, a constant (e.g., negligibly low) current may be provided at the electrochemical gas generator cell during the rest phase in order to reach the bias voltage at the electrochemical gas generator cell.

As an alternative, it is possible, for example, to use a potential (e.g., electrical bias voltage) close to the electrolysis potential of the electrochemical gas generator cell together with an impressed transient signal (e.g., interference or sinus signal, sawtooth signal or with offset). For example, it is also possible to provide during the rest phase a constant (e.g., negligibly low) current together with an impressed transient interference (=sinus, sawtooth or with offset) at the electrochemical gas generator cell.

The potential at a generator electrode (e.g., a gas generation electrode of the electrochemical gas generator cell) may preferably be set such that it remains lower than the electrolysis voltage during the rest phase. Provisions may be made, for example, for not switching off the electrolysis device altogether, but, e.g., to reduce its current to the lowest possible value.

Further details and aspects are described in connection with other examples explained above or below. The examples shown in FIG. 2 may have one or more optional, additional features, which correspond to one or more aspects, which are described above or below in conjunction with the concept proposed or with one or more examples (for example, in conjunction with FIG. 1 or FIGS. 3-7).

FIG. 3 shows a schematic view 30 of a charge Q₁ (e.g., according to other concepts) and Q₂ (e.g., according to concepts proposed in conjunction with FIGS. 1 and 2), which charge is available in two different operating modes of an electrochemical gas generator cell for generating gas. An operating current I_(gen) flows during an electrolysis period or operating phase (e.g., from time t_(on) to t_(off)) and a zero signal current I_(Ruhe) flows through the electrochemical gas generator cell during a rest phase.

The systems shown in FIGS. 1 and 2 may be used, for example, to test gas sensors (e.g., for so-called bump tests). When testing gas sensors by means of electrochemical gas generator cells, it may be advantageous to carry out a sensor test in the shortest possible time, because the sensor is not available, for example, for measuring and alarm functions during the testing time. It may therefore be necessary to keep the electrolysis times of the gas generator cells as short as possible. Such electrolysis time advantageously amount to a few seconds only.

When an electrochemical cell (e.g., the electrochemical gas generator cell 11) is switched on, for example, a so-called capacitive charging current flows at first over the gas generator cell electrodes to establish an electrochemical double layer in front of the electrodes (e.g., when the current source 12 is switched on at the time t_(on)). Moreover, surface reactions, e.g., the formation of an oxide layer or rearrangements of a hydrate layer and wetting reactions, which have a complex chemical nature depending on the electrode material being used and can be summed up for simplicity's sake as capacitive current together with the current flowing for building up the double layer, take place on the electrodes involved when such an electrochemical cell is switched on.

The percentage of this capacitive current relative to the total current, which flows during an electrolysis, rises with decreasing electrolysis time (e.g., shorter electrolysis time) and may be of considerable significance, for example, in case of electrolysis times in the lower range of seconds. In addition, the wetting of electrodes during the operation may change and it increases, e.g., because of energization and/or an applied potential. Reactions possibly taking place on the electrode surface, e.g., the coating of the electrode surface with hydroxyl ions and/or the coating of the surface with a solvation sheath, are exemplary processes that take place depending on the electrode potential and can come close again to a state of equilibrium for currentless conditions, for example, only slowly, e.g., within several hours to days after the switching off of an electrode. For example, a different chemical state is obtained concerning the electrode surface for each gas generation electrode corresponding to its past history (e.g., time elapsed since the last operating phase), which becomes noticeable especially in the wetting characteristic and hence in the active surface. As a result of this, a different percentage of capacitive charging current will flow corresponding to the past history and a residual percentage of current, which depends on the past history of the electrode, is obtained for the electrolysis proper and for the generation of test gas. This leads to the production of different quantities of test gas by a gas generator cell in some cases depending on recovery times (e.g., duration of the rest phase) between consecutive tests and on the conditions prevailing during this time (especially temperature and/or humidity of the ambient atmosphere).

These processes are shown schematically in FIG. 3 on the basis of the diagrams shown. The upper diagram 30 a shows the time curve of the cell current and the lower diagram 30 b shows the curve of the cell voltage (e.g., the voltage U_(gen) present at the electrochemical gas generator cell, e.g., voltage between the gas generation electrode and the counterelectrode). The curve describing the cell voltage, which curve is described in the above two paragraphs (e.g., with the use of other concepts for operating the generator cell), is always indicated by a solid line. A time t_(on) and a time t_(off) mark the start and the end of the on time of the electrolysis cell. The lower voltage (e.g., electrolysis voltage) for the start of the gas formation reaction, which voltage is necessary for the generation of gas, is reached at a time to (e.g., in concepts without the use of a bias voltage in the rest phase). The area (fine shading) marked as Q₁ in the upper diagram indicates the charge I_(gen) made available for the electrolysis proper. I_(gen) marks the electrolysis current predefined by an external current source. A voltage value U_(ocp) indicates the voltage that becomes established in the state of equilibrium without external current flow between the electrodes.

Insufficient reproducibility of the generation of gas by electrochemical gas generators is, e.g., unfavorable for testing sensors for proper function because the peak height as an indicator of the residual activity of the sensor is of particular significance in performance tests and/or may be linked directly with the quantity of test gas formed during the electrolysis. The charge Q₁ available for the test gas generation may decrease to zero in the extreme case and the test may fail (e.g., when the current I_(gen) provided is not sufficient to raise the cell voltage within the predefined time period to the value of the electrolysis potential).

The concepts being proposed here can be used to increase the cell voltage at the start of the electrolysis (e.g., application of the generator current) from an undefined voltage state (e.g., a random value between U_(ele) and U_(ocp)), and an electrical bias voltage U_(pre), can be applied to the cell (e.g., the electrochemical gas generator cell 11) between operating phases of the generator cell.

To maintain the electrode (gas generating electrode) in a possibly constant, preconditioned state, it is proposed that this electrode not be disconnected from the counterelectrode by switching off during the pauses between the bump tests. It is made possible that the electrode is always maintained in a, for example, constant state in respect to its wetting and its chemical surface activity, so that high capacitive charge current will flow uniformly in the sense of the above explanation (e.g., by maintaining the bias voltage at the electrochemical gas generator cell 11 during the rest phase). For example, the electrode is maintained in this case in a state that is as close as possible to the conditions of the later electrolysis, in order to keep this percentage of current low and thus to make short test times possible (e.g., the bias voltage U_(pre) may be lower than the electrolysis voltage U_(ele) only very slightly). As a result, the charge quantity available for the gas generation during the electrolysis time (charge Q₂ indicated by coarse shading) can be increased and/or it can be generated after the provision of the operating current I_(gen)) already earlier than in other concepts.

FIG. 4 shows a schematic view of a system 40 a with an electrochemical gas generator cell 11, with an electrical d.c. current source 12 a and with an adjustable voltage source 41. The microcontroller 13, the d.c. current source 12 a and/or the adjustable voltage source 41 may form a control device 40 of the system 40 a for controlling the electrochemical gas generator cell 11.

For example, a current source (e.g., d.c. current source 12 a or constant current source 12 a), which sends a current through the electrodes of the gas generator, is necessary for operating gas generators (e.g., the electrochemical gas generator cell 11). In order to make it possible to drive the current necessary for the electrolysis through the gas generator electrodes, for example, a potential difference is necessary between the gas generator electrodes. The value of the potential difference depends, for example, on the internal resistance and the underlying chemical reaction during the electrolysis taking place in the gas generator 11. The power consumption of the gas generator 11 is obtained from the product of the gas generator current gen and the potential difference U_(gen) between the electrodes of the gas generator. Values for typical power consumptions may be in a range of 0.1 mW (or of 0.5 mW, of 1 mW, of 1.5 mW or of 5 mW) to 10 mW (or up to 100 mW). For example, an electronic unit, which may advantageously comprise the microcontroller 13, is necessary for controlling and monitoring the current source 12 a of the gas generator 11. The gas generator electronic unit, comprising a current source 12 a and a microcontroller 13 (e.g., control device for operating the electrochemical gas generator cell 11), is supplied with energy by a gas-measuring device or a separate energy source, for example, a battery.

If the gas generator electronic unit is supplied with energy via a gas-measuring device, the maximum power consumption of the gas generator electronic unit and of the gas generator may be limited, e.g., on the basis of external requirements. With this limitation, some gas generators can only be operated with an increased technical and design effort. If the gas generator electronic unit is supplied via a separate energy source, the maximum operating time or the number of bump tests depends on the electrical capacity of the energy source. The maximum electrical capacity that can be supplied, e.g., within a measuring head design is limited, for example, based on size limitations. For example, regular charging operations or a regular replacement of energy storage devices is thus necessary. An energy-saving operation of the gas generator and of the gas generator electronic unit is therefore necessary in order to reduce or avoid charging and replacement cycles.

It is proposed that an adaptive adjustment of the supply voltage U_(cc) of the gas generator current source 12 a to the potential difference necessary for the electrolysis, which is predefined by the gas generator 11, be provided. As a result, it is possible, for example, to reduce the power loss of the system 40 a. For example, the necessity of replacing the battery can thus be reduced (or, for example, the need to replace or charge the energy source can thus be largely eliminated) in conjunction with an energy-efficient circuit technology.

An exemplary embodiment of the gas generator electronic unit with adaptive supply voltage and with gas generator 11 is shown in FIG. 4. The microcontroller 13 measures the gas generator potential U_(gen) and the gas generator current I_(gen) as a function of the voltage drop U_(IGen) at the current-measuring resistor 14. Depending on the measured values, the supply voltage U_(cc) of the d.c. current source 12 a through the adjustable voltage source 41 is adjusted by the microcontroller 13 and the gas generator current I_(gen) is adjusted by changing desired variables (e.g., desired voltage U_(cc-set) and desired current I_(G-set)).

For example, the desired voltage U_(cc-set) may be selected to be somewhat higher than the electrolysis voltage of the electrochemical gas generator cell 11. For example, a repeated measurement of a current electrical voltage (e.g., a continuous measurement or a measurement quantized over time) during an operating phase of the electrochemical gas generator cell 11 can be used to detect changes in the electrolysis voltage of the electrochemical gas generator cell 11 and/or to correspondingly adaptively adjust the regulation of the supply voltage U_(cc) to the current electrolysis voltage.

Further details and aspects are described in connection with examples explained above or below. The examples shown in FIG. 4 may have one or more optional, additional features, which correspond to one or more aspects, which are described above or below in conjunction with the proposed concept or with one or more examples (for example, in connection with FIG. 1-3 or 5-7).

FIG. 5 shows a flow chart of a process 50 for operating a generator cell. The process 50 comprises the application 51 of an electrical current to the electrochemical gas generator cell during an operating phase in order to increase a voltage at the electrochemical gas generator cell at least to the electrolysis voltage. The process 50 further comprises a reduction 52 of the electrical current to a zero signal current during a rest phase in order to stop the generation of gas. An electrical bias voltage, which is lower than the electrolysis voltage and amounts to at least 60% of the electrolysis voltage, is obtained in this case based on the zero signal current during the rest phase at the electrochemical gas generator cell.

The gas generator cell is maintained in a defined state of readiness (e.g., setting of the electrical bias voltage at the gas generator) by means of a special electronic control (e.g., control device proposed) during the pauses of the generator (e.g., rest phase). For example, the reproducibility and/or the speed of bump tests can be increased hereby.

Further details and aspects are described in conjunction with other examples explained above or below. The examples shown in FIG. 5 may correspond to one or more aspects, which are described above or below in connection with the proposed concept or with one or more examples (for example, in connection with FIG. 1-4 or 6-7).

FIG. 6 shows a flow chart of a process 60 for operating a generator cell. The process 60 comprises the application 61 of an electrical current to the electrochemical gas generator cell by means of a d.c. current source during an operating phase in order to generate the gas, and the setting 62 of a supply voltage of the d.c. current source to a value of at most 125% of a voltage present at the electrochemical gas generator cell.

The supply voltage of the gas generator and of the gas generator electronic unit can be reduced hereby, e.g., during bump tests (e.g., operating phase of the electrochemical gas generator cell) to reduce power loss (e.g., adaptive adjustment of the supply voltage).

The voltage supply of the constant current source (e.g., d.c. current source) may be set, e.g., in a data set, in anticipation to a typical value. This procedure may additionally save energy, because a regulation of the supply voltage can be reduced (e.g., it is not necessary to set first the maximum supply voltage of the constant current source and to subsequently regulate the voltage down).

For example, the potential difference at the gas generator can further be measured, so that, for example, the state of the gas generator can be inferred. Additional electrodes (e.g., a plurality of generator electrodes, a reference electrode; and/or auxiliary electrodes for multistage reactions) may be present or used in the gas generator. The voltage adjustment may be carried out several times, e.g., cyclically during the gas generation.

Further details and aspects are described in conjunction with examples explained above or below. The examples shown in FIG. 6 may have one or more optional, additional features, which correspond to one or more aspects, which are described above or below in conjunction with the proposed concept or with one or more examples (for example, in conjunction with FIG. 1-5 or 7).

FIG. 7 shows a flow chart of an exemplary process 70 for the adaptive setting of a supply voltage of a current source for operating an electrochemical gas generator.

An exemplary bump test cycle is shown in FIG. 7. The bump test is started by a trigger (e.g., start 71 of the process 70). The trigger may be triggered by an external or internal event (e.g., triggering 72). The microcontroller (e.g., microcontroller 13) is switched thereby from the sleep mode (e.g., reduced energy consumption and reduced functionality) into the normal mode (normal operating mode, e.g., operating phase) (e.g., switching 73 of the operating mode). The microcontroller 13 activates the voltage supply (e.g., CC source) (e.g., activation 74 of the voltage supply) of the constant current source (e.g., current source 12 a) and it sets at first, e.g., the maximum possible value therefor. The constant current source is then switched on corresponding to the specification of the desired value I_(G-set) (e.g., switching on 75 of the current source), and a current flows through the gas generator. A characteristic potential, which is measured by the microcontroller (e.g., measurement 76 of the voltage U_(gen)), becomes established due to the current flow at the gas generator.

A low offset, which is, for example, in the range of 5%-25% of the measured value, may be added to the measured potential value. The voltage thus calculated represents the value to be made available for supplying the gas generator current source. The microcontroller 13 can bring about the setting of a corresponding supply voltage of the gas generator current source (e.g., setting 77 of the supply voltage). The supply voltage may be maintained, e.g., until the test time (e.g., electrolysis time) has expired (e.g., a testing 78 of the test time already carried out may take place in this respect). After the end of the bump test time (e.g., CC time) set in anticipation, the microcontroller is again put into the sleep mode (e.g., activation 79 of the sleep mode), and a next bump test can be triggered, e.g., as described above.

A plurality of features or individual features, which are shown on the basis of the process 70 in combination with FIG. 7, may also be used, for example, in processes proposed above (e.g., the process 50 described in conjunction with FIG. 5) or the process 60 described in conjunction with FIG. 6).

One aspect of the present invention pertains to an activation principle for a generator electrode of a gas generator. Another aspect of the present invention pertains to a process for optimizing the energy consumption during the operation of gas generators.

The present disclosure pertains to an advantageous operation of electrochemical gas generators. These are used, e.g., in a so-called bump test for testing sensors and they generate in the process, if needed, a gas (e.g., test gas) for testing the ability of the sensors (e.g., gas sensors) to function.

Circuits and modes of operation for electrochemical gas generators for generating test gas as rapidly and reproducibly as possible, e.g., in connection with the performance testing of gas sensors are proposed. Further, circuits and modes of operation are proposed for the energy-efficient operation of electrochemical gas generator cells.

The aspects and features that are described together with one or more of the examples and figures described in detail above may also be combined with one or more of the other examples in order to replace an identical feature of the other example or in order to additionally introduce the feature into the other example.

Examples may be or pertain, furthermore, to a computer program with a program code for carrying out one or more of the above processes when the computer program is run on a computer or processor. Steps, operations or processes of different processes described above may be carried out by programmed computers or processors. Examples may also cover program storage devices, e.g., digital data storage media, which code machine-readable, processor-readable or computer-readable and code machine-executable, processor-executable or computer-executable programs of instructions. The instructions execute some or all of the steps of the above-described processes or cause them to be executed. The program storage devices may comprise or be, e.g., digital memories, magnetic storage media, for example, magnetic disks and magnetic tapes, hard drives or optically readable digital data storage media. Further examples may also cover computers, processors or control units, which are programmed for executing the steps of the above-described processes, or (field) programmable logic arrays ((F)PLAs=(Field) Programmable Logic Arrays) or (field) programmable gate arrays ((FPGA=(Field) Programmable Gate Arrays), which are programmed for executing the steps of the above-described processes.

Only the principles of the disclosure are described by the description and the drawings. Furthermore, all the examples mentioned here shall be used basically expressly for purposes of illustration only in order to support the reader in understanding the principles of the disclosure and the concepts contributed by the inventor(s) for improving the technique. All the statements made here concerning the principles, aspects and examples of the disclosure as well as concrete examples thereof comprise their corresponding examples.

A function block called “means for . . . ” carrying out a certain function may pertain to a circuit, which is configured to carry out a certain function. Thus, “means for something” may be implemented as “means configured for or suitable for something,” e.g., a component or a circuit configured for or suitable for the respective object.

Functions of different elements shown in the figures, including each function block called “means for providing a signal,” “means for generating a signal,” etc., may be implemented in the form of dedicated hardware, e.g., “a signal provider,” “a signal processing unit,” “a processor,” “a control,” etc., as well as hardware capable of executing software in conjunction with corresponding software. In case of provision by a processor, the functions may be provided by an individual dedicated processor, by an individual processor used jointly or by a plurality of individual processors, some of which or all of which may be used jointly. However, the term “processor” or “control” is far from being limited to hardware capable of exclusively executing software, but it may comprise digital signal processor hardware (DSP hardware; DSP=Digital Signal Processor), network processor, application-specific integrated circuit (ASIC=Application Specific Integrated Circuit), field-programmable gate array (FPGA=Field Programmable Gate Array), read-only memory (ROM=Read Only Memory) for storing software, random access memory (RAM=Random Access Memory) and nonvolatile storage device (storage). Other hardware, conventional and/or customer-specified, may also be included.

A block diagram may represent, for example, a coarse circuit diagram, which implements the principles of the disclosure. Similarly, a flow chart, a process diagram, a state transition diagram, a pseudocode and the like may represent different processes, operations or steps, which are represented essentially in computer-readable medium and are thus executed by a computer or processor, regardless of whether such a computer or processor is explicitly shown. Processes disclosed in the description or in the patent claims may be implemented by a component, which has means for carrying out each of the respective steps of these processes.

It is apparent that the disclosure of a plurality of steps, processes, operations or functions disclosed in the description or in the claims shall not be interpreted as being configured as being in the sequence described, unless this is otherwise explicitly or implicitly indicated, e.g., for technical reasons. Therefore, these are not limited to a certain sequence by the disclosure of a plurality of steps or functions, unless these steps or functions are not interchangeable for technical reasons. Further, an individual step, function, process or operation may include in some examples a plurality of partial steps, partial functions, partial processes or partial operations and/or can be broken up into these. Such partial steps may be included and be a part of the disclosure of this individual step, unless they are explicitly ruled out.

Furthermore, the following claims are hereby included in the detailed description, where each claim may represent a separate example in and of itself. While each claim may stand as a separate example in and of itself, it should be noted that—even though a dependent claim may pertain in the claims to a certain combination with one or more other claims—other examples may also comprise a combination of the dependent claim with the subject of any other dependent or independent claim. Such combinations are proposed here explicitly, unless it is stated that a certain combination is not intended. Further, features of a claim may also be included for every other independent claim, even if this claim is not made directly dependent upon the independent claim.

While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles. 

What is claimed is:
 1. An electrochemical gas generator cell control device for actuating an electrochemical gas generator cell, wherein the control device is configured: to output an operating phase control signal, for an operating phase of the electrochemical gas generator cell, which brings about a generation of an electrical operating voltage at the electrochemical gas generator cell, wherein the electrical operating voltage is at least equal to an electrolysis voltage of the electrochemical gas generator cell; and to output a rest phase control signal, for a rest phase of the electrochemical gas generator cell, which brings about a generation of an electrical bias voltage at the electrochemical gas generator cell, wherein the electrical bias voltage is lower than the electrolysis voltage.
 2. An electrochemical gas generator cell control device in accordance with claim 1, wherein the control device is configured to set the electrical bias voltage at at least 60% of the electrolysis voltage.
 3. An electrochemical gas generator cell control device in accordance with claim 1, wherein the control device is configured to generate the electrical bias voltage at the electrochemical gas generator cell during at least 50% of the rest phase.
 4. An electrochemical gas generator cell control device in accordance with claim 1, wherein the rest phase control signal is constant over time.
 5. An electrochemical gas generator cell control device in accordance with claim 1, wherein the rest phase control signal has an alternating component.
 6. An electrochemical gas generator cell control device in accordance with claim 1, wherein the electrical bias voltage is lower by at least 300 mV and is lower by at most 1.5 V than the electrolysis voltage of the electrochemical gas generator cell.
 7. An electrochemical gas generator cell control device in accordance with claim 1, wherein: the operating phase control signal comprises a first current signal for the electrochemical gas generator cell and the rest phase control signal comprises a second current signal for the electrochemical gas generator cell; and the second current signal has a current intensity of at most 1% of a current intensity of the first current signal.
 8. An electrochemical gas generator cell control device in accordance with claim 1, wherein the rest phase control signal comprises a current signal, which has a mean value of at least 10 nA and at most 10 μA.
 9. An electrochemical gas generator cell control device in accordance with claim 1, further comprising: a current source for generating the operating phase control signal as an operating current for the electrochemical gas generator cell; a voltage source for generating the second control signal as an electrical bias voltage; and a switch configured for switching an electrical connection from a connection between the current source and the electrochemical gas generator cell to a connection between the voltage source and the electrochemical gas generator cell.
 10. An electrochemical gas generator cell control device in accordance with claim 9, wherein a mean output voltage of the voltage source is lower than the electrolysis voltage and equals at least 60% of the electrolysis voltage.
 11. An electrochemical gas generator cell control device in accordance with claim 1, further comprising a measuring device for measuring an electrical voltage present at the electrochemical gas generator cell.
 12. An electrochemical gas generator cell control device in accordance with claim 1, further comprising: a d.c. current source for generating an operating current for the electrochemical gas generator cell; and a voltage supply of the d.c. current source, wherein the control device is configured to regulate a supply voltage of the voltage supply to a predefined value of at most 125% of a voltage present at the electrochemical gas generator cell.
 13. A system for operating an electrochemical gas generator cell, which is configured to generate a gas when an electrical voltage higher than an electrolysis voltage of the electrochemical gas generator cell is applied, the system comprising: a d.c. current source, configured to apply an operating current to the electrochemical gas generator cell; a voltage supply of the d.c. current source; and a control device for controlling the voltage supply of the d.c. current source, wherein the control device is configured to regulate a supply voltage provided by the voltage supply during an operation of the electrochemical gas generator cell to a predefined value of at most 125% of the voltage present at the electrochemical gas generator cell.
 14. A system in accordance with claim 13, further comprising a measuring device for measuring the electrical voltage present at the electrochemical gas generator cell.
 15. A system in accordance with claim 14, wherein the control device is configured to adjust the supply voltage on the basis of a voltage measurement provided by the measuring device during an operating phase of the electrochemical gas generator cell.
 16. A system in accordance with claim 13, the control device further comprising a memory, on which the predefined value of the supply voltage is stored or is storable.
 17. A system in accordance with claim 13, wherein the system is configured to generate a zero signal current of less than 300 nA and an operating current of at least 1 mA for application to the electrochemical gas generator cell.
 18. A system for generating a gas, the system comprising: an electrochemical gas generator cell comprising a number of x generator electrodes and a number of y counterelectrodes, wherein x and y are natural numbers; and an electrochemical gas generator cell control device for actuating the electrochemical gas generator cell, wherein the control device is configured: to output an operating phase control signal, for an operating phase of the electrochemical gas generator cell, which brings about a generation of an electrical operating voltage at the electrochemical gas generator cell, wherein the electrical operating voltage is at least equal to an electrolysis voltage of the electrochemical gas generator cell; and to output a rest phase control signal, for a rest phase of the electrochemical gas generator cell, which brings about a generation of an electrical bias voltage at the electrochemical gas generator cell, wherein the electrical bias voltage is lower than the electrolysis voltage.
 19. A process for operating an electrochemical gas generator cell, which is configured to generate a gas in the presence of an electrical voltage higher than an electrolysis voltage of the electrochemical gas generator cell, the process comprising: applying an electrical current to the electrochemical gas generator cell during an operating phase in order to increase a voltage at the electrochemical gas generator cell at least to the electrolysis voltage; and reducing the electrical current to a zero signal current during a rest phase in order to stop the generation of gas, wherein an electrical bias voltage, which is lower than the electrolysis voltage and amounts to at least 60% of the electrolysis voltage, is obtained on the basis of the zero signal current during the rest phase at the electrochemical gas generator cell.
 20. A process for operating an electrochemical gas generator cell, which is configured to generate a gas in the presence of an electrical voltage higher than an electrolysis voltage of the electrochemical gas generator cell, the process comprising: applying an electrical current to the electrochemical gas generator cell by means of a d.c. current source during an operating phase in order to generate the gas; and the setting of a supply voltage of the d.c. current source to a value of at most 125% of a voltage present at the electrochemical gas generator cell. 